Device for exchanging electron sources in electrical discharge devices



Nov. 4, 1969 smmmo KATAGIRI E AL ,9

DEVICE FOR EXCHANGING ELECTRON SOURCES IN ELECTRICAL DISCHARGE DEVICESFiled April 5, 1968 2 Sheets-Sheet .1

F /63 FR/OR ART I INVENTOR JIIIIYT/IZ 0 4 r4 4 m I you/I 01:4 NA/,4 an#4 BY 2 AM ATTORN Y;

Nov. 4, 1969 sn-ummo KATAGIRI L 3,476,972

DEVICE FOR EXCHANGING ELECTRON SOURCES IN ELECTRICAL DISCHARGE DEVICESFiled April 5, 1968- I 2 Sheets-Sheet 2.

INVENTORS JAII/VJIR a 1m mam BY 6%,; g

ATTORNEY;

United States Patent 3,476,972 DEVICE FOR EXCHANGING ELECTRON SOURCES INELECTRICAL DISCHARGE DEVICES Shinjiro Katagiri and Yoshihisa Minamikawa,Katsutashi, Japan, assignors to Hitachi, Ltd., Tokyo, Japan, acorporation of Japan Filed Apr. 5, 1968, Ser. No. 719,023 Claimspriority, application Japan, Apr. 12, 1967,

42/22,898 I 1 Int. Cl. H01j 1/02, 9/02 us. or. 313-237 3 Claims ABSTRACTOF THE DISCLOSURE BACKGROUND OF THE INVENTION This inventionrelates to adevice for exchanging articles in high-pressure vessels, and moreparticularly to an improvement in the structure of a device of the kinddescribed for preventing the danger of bursting that might occur in thevessel. v v

In an apparatus such as a high voltage charged particle accelerator ofconventional construction, it is common practice to enclose associatedequipment such as a high voltage supply and an accelerating tube sectionwithin a metallic tank for the purpose of minimizing any danger to humanbeings and to reduce the space required for installation. The tank isthen filled with an insulating gas at a high pressure above oneatmosphere in order to provide a high degree of insulation. When aheated filament, for example, is used as an electron source in such anapparatus, there may arise a necessity of exchanging the same for anewone in the event of'the breakdown or deterioration of such afilament. According to a conventional manner of replacing such afilament, the metallic tank is detached from the apparatus to expose andexchange the defective electron source whichi's disposed on the top ofthe accelerating tube. This exchanging operation of the electron source,however, involves troublesome manipulations including dismounting andremounting of the tank as well as increased costs due to loss of theinsulating gas. In order toovercome the above drawbacks and otherdifficulties, an article exchanging device such as, for example, onedisclosed inU'nited States Patent No. 3,268,759 has been employedhitherto.

The device for exchanging articles disclosed in the United States patenthas a structure as shown in' FIG. 1. Referring to FlG., 1; a highvoltage charged particle accelerator comprises an accelerating tube 1 onthe top of which an electron source 2 or an electron gun is mounted bymeans of a supporting member 3 of annular shape for supporting thereonthe electron source 2. The accelerating tube 1 is surrounded by a highvoltage supply 4, and all these accelerator elements are contained in ametallic tank or vessel 5 the interior of which is maintained at a highpressure with a gas of insulating nature such as sulfur hexafluoride,Freon or the like enclosed therein. In order to ensure a gas-tightrelationship between the high pressure portions of the apparatus filledwith the insulating gas and the accelerating tube 1 whose interior ismaintained in a high vacuum condition, a

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rubber gasket 6 is disposed at a portion where the electron source 2 isfitted to the supporting member 3.

The device for exchanging articles comprises a generally cylindricalmember 7 which is disposed on the top of the metallic vessel 5 on theside opposite the electron source 2 and movable into and out of themetallic vessel 5 to move toward and away from the electron source 2.The cylindrical member 7 has an internal diameter of such a dimensionthat the electron source 2 can be adequately accommodated therewithin.When urged inwardly into the vessel 5 toward the electron source 2, thatis, toward the article exchanging position, the cylindrical member 7finally abuts the supporting member 3 on the top of the acceleratingtube 1 in a manner that the lower annular face thereof encircles theelectron source 2. The inwardly urged or lowered position of thecylindrical member 7 is shown by dotted lines 7'. A rubber gasket 8maintains a gas-tight relationship in the abutting area between thelower annular face of the cylindrical member 7 and the supporting member3 at the lowered position of the cylindrical member 7, and a rubbergasket 9 maintains a gas-tight relationship in the abutting area betweenthe vessel wall and the outer peripheral surface of the cylindrical.member 7 at any position of the cylindrical member 7. A piston 10 isvertically slidably disposed within the cylindrical member 7 and has aplurality of recesses 11 bored in the bottom thereof, which recesses 11have such a configuration that they will snugly fit over a plurality ofprojections or pins 13 of complementary configuration provided on theelectron source 2 so as to carry the electron source 2 with the piston10 for the exchanging operation. A rubber gasket 12 maintains agas-tight relationship at all times in the abutting area between theperipheral surface of the piston 10 and the inner wall of thecylindrical member 7. The electron source 2 is surrounded by a coronashield 14 for high voltage.

In operation for th exchange of the electron source 2 with the articleexchanging device having the structure described above, the cylindricalmember 7 is actuated by a suit-able external means (not shown) to belowered from the normal inoperative position shown by solid lines and isfinally secured at the position of dotted lines 7, where the lower faceof the cylindrical member 7 bears against the rubber gasket 8 disposedon the supporting member 3 mounting thereon the electron source 2. Theinterior of the cylindrical member 7 is thereby isolated from thesurrounding gas chamber and any flow of gas thereinto is positively shutofi, thus establishing an isolated article exchanging passage within thevessel 5. Under this condition, application of high voltage is stoppedand atmospheric pressure is supplied into the accelerating tube 1. Thepiston 10 is then lowered by a suitable means (not shown) until therecesses 11 fit on the pins 13 provided on the electron 2 for carryingthe defective electron source 2 with the piston 10. The piston 10'carrying thereon the electron source 2 is subsequently pulled upwardlyto take out the electron source 2. A new electron source 2 is fitted onthe bottom of the piston 10 in place of the defective one, and thepiston 10 is again lowered within the cylindrical member 7 to mount thenew electron source 2 at the predetermined position on the supportingmember 3 at the top of the accelerating tube 1 to complete theexchanging operation.

It will be recalled that the insulating gas is enclosed within thevessel 5 at a high pressure above one atmosphere, and the cont-act areabetween the vessel wall and other outer peripheral surface of thecylindrical member 7 is maintained in the gas-tight relationship by therubber gasket 9. Accordingly, in such an article exchanging device, thepower of an electric motor or the like must be used in order to lowerthe cylindrical member 7 since a considerably large force is required tocause the downward movement of the cylindrical member 7. Furthermore,the operation of the kind described above which must be carried outunder such a high pressure condition is very dangerous in view of aliability to giving rise to a bursting accident due to erroneousmanipulation, and the operation also requires a considerable degree ofskill.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to obviate the occurrence of a bursting or like dangerousaccident in an article exchanging operation within the high-pressurevessel of the kind described above.

Another object of the present invention is to provide convenient meansof very simple structure for preventing the occurrence of a dangerousaccident as described above.

A further object of the present invention is to provide means forrelieving the shock imparted to the supporting member when thecylindrical member abuts the supportin g member in the articleexchanging operation.

Still another object of the present invention is to provide means forre-collecting or recovering the insulating gas prior to the articleexchanging operation.

In accordance with the present invention which attains the variousobjects described above, there is provided a device for exchanging anarticle in a vessel filled with a gas at high pressur having a tubularmember and article exchanging means, said tubular member being adaptedto slide through an opening in the wall of said high-pressure vessel sothat at the innermost position of said tubular member the end facethereof engages a fixed supporting member within said vessel upon whichsaid article to be exchanged is mounted, said tubular member being in agas-tight sealed relationship within said high-pressure vessel, saidarticle exchanging means being adapted to effect the exchange of saidarticle through said tubular member; wherein the improvement whichcomprises at least one annular member having a slit to permit leakagetherethrough of the gas in said vessel, said annular member beingdisposed at a gap between said tubular member and said opening in thewall of said vessel, and at least one sealing member for keeping thegas-tight sealed relationship between said tubular member and saidvessel, said sealing member being disposed in the abutting area betweenthe upper face of the outer part of the lower end portion of saidtubular member and the lower peripheral face of said opening in the wallof said vessel at the outermost position of said tubular member.

These and other objects, advantages and features of the presentinvention will become obvious from the following description withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic sectionalview through the principal parts of a high voltage charged particleaccelerator equipped with the prior art article exchanging devicedescribed previously.

FIG. 2 is a diagrammatic sectional view through the principal parts of ahigh voltage charged particle accelerator equipped with an articleexchanging device embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved device embodyingthe present invention comprises a generally tubular or cylindricalmember 7 which is slidably received in an opening in the wall of ahigh-pressure vessel 5 with a very narrow annular gap 16 definedtherebetween. The cylindrical member 7 is movable toward and away from afixed supporting member 3 supporting thereon an electron source 2 whichis mounted on the top of an accelerating tube 1. The outer part of thelower end portion of the cylindrical member 7 is flanged as at 21, and agasket 8 of rubber or like material maintains a gas-tight relationshipbetween the lower face of the flanged outer part of the lower endportion 21 of the cylindrical member 7 and the supporting member 3 atthe lowered position of the cylindrical member 7.

Two rings 15 for guiding the sliding movement of the cylindrical membereach having a very fine slit (not shown) therein are disposed at the gap16 defined between the cylindrical member 7 and the opening in the wallof the vessel 5 so as to allow for free leakage of an insulating gas inthe vessel 5 through the slits at the time when the electron source isexchanged. A removable lid 17 closes the central aperture in the endportion of the cylindrical member 7, and a gasket 18 of rubber or likematerial maintains a gas-tight relationship between the lid 17 and theinner wall of the cylindrical member 7. The lid 17 may be removed whenit is desired to exchange the electron source 2 for a new one, and asuitable means (not shown) may be inserted through the cylindricalmember 7 to effect the desired article exchanging operation. A gasket 19of rubber or like material is disposed on the upper face of the flangedouter part of the lower end portion 21 of the cylindrical member 7 inorder that it engages the lower peripheral face of the opening in thewall of the vessel 5 at the normal outermost position of the cylindricalmember 7 in order to thereby maintain a gas-tight relationship betweenthe vessel 5 and the cylindrical member 7. A device 20 for re-collectingthe gas in the vessel 5 is suitably connected to the latter as shown.

When not in article exchanging operation, the cylindrical member 7 iskept at its outermost position at which the upper face of the flangedouter part of the lower end portion 21 thereof engages the lowerperipheral face of the opening in the wall of the vessel 5, and theinsulating gas is sealed at high pressure within the vessel 5 by thegaskets 18 and 19. The gasket 19 may be disposed on the lower peripheralface of the opening in the wall of the vessel 5 in the abutting areabetween such a face and the upper face of the flange outer part of thelower end portion 21 of the cylindrical member 7 in place of theillustrated position on the flanged outer part of the lower end portion21. In the article exchanging operation, the cylindrical member 7 islowered from its normal non-operative position shown by solid lines toits innermost position as shown by dotted lines to establish an articleexchanging passage. The lid 17 is then removed and the articleexchanging means is inserted into the cylindrical member 7 to effect thedesired article exchanging operation. Since, in such an operation, thegas in the vessel 5 leaks outwardly through the slit in the rings 15 andthrough the gap 16 as the cylindrical member 7 is lowered from itsoutermost position, the cylindrical member 7 can easily be lowered intothe vessel 5 without being encountered with any resistance, thuseliminating the need for the use of electrical driving power or the likein the prior art device while utterly obviating the danger of a burstingaccident or the like pointed out previously. Furthermore, a very smallamount of atmospheric air can only flow into the vessel 5 or a verysmall amount of gas can only flow out of the vessel 5 because the slitand the gap 16 are very narrow and thus the atmospherie air can onlycontact with the gas in a very small area. The allowable amount of gasthat may leak out of the vessel 5 can be minimized when a gas having aspecific gravity higher than that of atmospheric air is employed.

Furthermore, in view of the fact that a pressure at substantially theatmospheric pressure prevails within the vessel 5 during the articleexchanging operation, the gasket 8 need not be of special gas-tightgrade and may be dispensed with. Even with the absence of the gasket 8,the mixture between the gas and the atmospheric air at this portionwould be quite negligible. The gasket 8 may preferably have a cushioningelfect in order to prevent damage to the supporting member 3 when thelatter is abutted by the cylindrical member 7, and in this respect, thegasket 8 may preferably be made of sponge rather than rubber.

The means for taking out the article through the cylindrical member 7may be a piston 10 employed in the prior art device or may be any othersuitable means. For example, the lid 17 is removed and a rod of suitablelength having a hook at one end thereof may be inserted into thecylindrical member 7 so that the article such as an electron source maybe hooked thereby to be taken out of the vessel 5. Where the internalpressure of the vessel 5 is considerably high, the gas re-collectingdevice 20 may be operated to re-collect or recover the gas in the vessel5 prior to the article exchanging operation so as to reduce the internalpressure to approximately the atmospheric pressure, and then the articleexchanging operation described above may be made to advantage.

From the foregoing description, it will be appreciated that the improveddevice according to the present invention has remarkable practicaladvantages over the prior art device in that the possibility ofoccurrence of a bursting accident or like danger is completelyeliminated and an article such as an electron source can very easily beexchanged.

We claim:

1, In combination with a device for exchanging an article in a vesselfilled with a gas at high pressure having a tubular member and articleexchanging means, said tubular member being adapted to slide through anopening in the Wall of said high-pressure vessel so that at theinnermost position of said tubular member the end face thereof engages afixed supporting member within said vessel upon which said article to beexchanged is mounted, said tubular member being in a gas-tight sealedrelationship within said high-pressure vessel, said article exchangingmeans being adapted to effect the exchange of said article through saidtubular member; the improvement which comprises at least one annularmember having a slit to permit leakage therethrough of the gas in saidvessel, said annular member being disposed at a gap between said tubularmember and said opening in the wall of said vessel, and at least onesealing member for keeping the gas-tight sealed relationship betweensaid tubular member and said vessel, said sealing member being disposedin the abutting area between the upper face of the outer part of thelower end portion of said tubular member and the lower peripheral faceof said opening in the wall of said vessel at the outermost position ofsaid tubular member.

2. A device according to claim 1, which further comprises a sealingmember disposed on the supporting member so as to absorb the shockimparted to the latter when the tubular member is caused to contact withthe supporting member.

3. A device according to claim 1, which further comprises means forre-collecting the gas in the high-pressure vessel.

References Cited UNITED STATES PATENTS 3,268,759 8/1966 Minamikawa313-337 2,319,061 5/1943 Hillin 250-460 2,218,886 10/1940 Krause 25027.52,301,955 11/1942 Krause 250-275 JOHN W. HUCKERT, Primary Examiner B.ESTRIN, Assistant Examiner US. Cl. X.R. 313236

